In the field of munitions it is often necessary to attack targets which are armored so that simple explosion of a munition against the armor is not sufficient to disable the target.
For such uses there have been developed projectiles known as "penetrators" which are not explosive, but are of density, configuration, and propulsion for maximum penetration force. One such device is known as a "long rod penetrator": it is of tungsten and is of relatively small diameter compared to its length, and extends along an axis from a forward aerodynamic point to a rearwared stabilizing fin structure. In order to obtain a high degree of propulsion the penetrators are arranged for firing from cartridge cases of several times the diameter of the penetrator, the case initially enclosing the rear portion of the penetrator including the fin structure. The mouth of the cartridge case must be large enough to pass the fin structure, so a sabot is fitted to the mid portion of the penetrator to initially close the mouth of the cartridge case and subsequently guide the penetrator down the barrel of the discharging cannon. The sabot and the fin structure contribute nothing to the penetrating power of the projectile, but add to the mass which must be accelerated from the cannon, and hence decrease the nozzle velocity obtainable for any given propulsion charge. The sabot is designed for aerodynamic disintegration when the penetrator leaves the cannon barrel, but the fin structure must remain functional during the flight of the projectile.